SNR-MC interactions have been intensively studied by observations of the shocked regions by using both molecular and atomic gas tracers (see e.g., [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [22]}, [23]}, [24]}, [25]}, [26]}, [27]}, [28]}, [29]}, [30]}).
Commonly, the rovibrational lines of H\(_{2}\)  and CO are notably used to characterize the SNR shocks. With no permanent dipole moment, H\(_{2}\)  is excited at high levels of excitation energy, which is optimally probed in early regions in shock. Owing to a dipole moment,
CO complements H2 by probing the cooler and denser part in the shocked regions.
Both the excitation diagram ("Boltzmann plot"), relation between the column density of the rotationally excited levels and their energy above the ground state , e.g., [24]}, [25]}), and the resolved velocity profiles (e.g., [28]}, [30]}) have been used to constrain the physical properties of the shocked gas.
